Double shutter and driving mechanism therefor



May 17, 1932. A. DINA 1,858,239

DOUBLE SHUTTER AND DRIVING MECHANISM THEREFOR 2 Sheets-Sheet 1 Filed May 29, 1950 INVENTOR May 17, 1932. A. DINA DOUBLE SHUTTER AND DRIVING MECHANISM THEREFOR Filed May 29, 1930 2 Sheets-Sheet 2 ATTORNEYS and at equal speed, and so Patented May 17, 1932 UNITED STATES PATENT OFFICE AUGUSTO DINA, OF ELIZABETH, NEW JERSEY, ASSIGNOR TO INTERNATIONAL YRO- NEW YORK, N. Y., A

J'ECT'OR CORPORATION, OF

CORPORATION OF DELAWARE DOUBLE SHUTTER AND DRIVING MECHANISM THEREFOR Application filed May 29, 1930. Serial No. 456,956.

This invention relates to gearing and has especial reference to gear trains and a method of developing them and is particularly concerned with the development of epicyclic gear trains which may be used in connection with the driving of shutters on motion picture machines, or for such other uses as desired.

A main object of the invention is to provide a simple, compact, centrally balanced train of gears which will drive desired apparatus with minimum of friction, noise, and vibration.

A further object is to present a method for the designing or development of such a train of gears by which many former seemingly insurmountable conditions may be overcome.

A still further object is to design a simple, compact, well balanced train of epicyclic gears for driving a pair of shutters in opposite directions on a moving picture machine designed that there is minimum of vibration, friction, and noise due to the new discovery of the method of designing such gears.

Further and more specific objects, features, and advantages will more clearly appear from the detailed description given below when taken in connection with the accompanying drawings which form part of the specification and which illustrate one present preferred form of the invention.

Broadly speaking, one feature of the invention includes a compound train of gears, preferably epicyclic, in which at least one pair of engaged gears of the train is formed with spiral teeth. and where the occasional impossibility of finding sets of gears whose diameters and teeth numbers will match, for any given center distance may be avoided.

Another point involved in the invention is to provide a compound epicyclic gear train in which the respective gear ratios such as and in which the respective values of a to b and 0 are r22 an 1 an 1 respectively. It has been found that these particular ratios when employed for the especial form of epicyclic trains where two shutter shafts are to be driven in opposite directions at the same speed, frictionless and vibrationless operation. The development of these broad ideas will follow in the specification.

The present preferred form of the invention is shown in the drawings of which,

Fig. 1 is a transverse vertical section taken on the line 11 of Fig. 2;

Fig. 2 is a longitudinal vertical section taken on the line 2-2 of Fig. 1;

give smooth, quiet, i c

and,

Fig. 4 is a transverse vertical section taken on the line 44 of Fig. 3.

As shown in the drawings and as contemplated by the breadth of the invention, there is provided a simple compact and efficient driving mechanism for a plurality of shutters. In the form shown in the drawings these shutters are shown as two which rotate in opposite directions and in this instance at the same speed for the purposes desired which may be to cut down the time of opening and closing the beam of projection light in a projector machine or in a camera, or other light transmitting machine.

The particular form of the invention shown is mounted on a suitable support 10, which may be a part or connected to a part of the frame of the projector or machine on which the shutter operates. This support 10 has a journal 11 in which is disposed a sleeve 12 one end of which is threaded and receives a nut 13 to tighten it in the journal 11 and the other end of which is preferably integrally formed as a gear 14:. This gear is therefore preferably stationary.

Disposed within the sleeve 12 there is a shaft 15 to which is fastened a hub 17 having a disc or plate 16 thereon. This disc has spaced sleeves 18 and 19 disposed thereon on opposite sides of the center of the disc. In these sleeves 18 and 19 are disposed shafts 20 and 21 rotatable therein. On one end of the shafts 20 and 21 there are disposed and fastened gears 22 and 23 which engage with the stationary gear 14. On the other ends of the shafts 20 and 21 are disposed and fastened or formed integral therewith gears 24 and 25.

Disposed loosely on the shaft 15 in front of the disc 16 is a hub 28 on which are disposed and formed a gear 29 and a disc 30. The gear 29 meshes with the oppositely disposed gears 24 and 25. The discs 16 and 30 have shutter blades 26, 27, 31 and 32 disposed thereon in the usual manner and relation. The disc 30 and the hub 28 are held in position on the shaft 15 by means of the retaining collar 28a.

This brief description of the actual structure of the train which constitutes the preferred present form of the invention indicates that the shutters 26 and 31 rotate in opposite directions and supposedly at the same speed.

How these factors were achieved in the production of such a simple, compact, and well balanced structure is a matter which will now be considered. As far as the gear train is concerned, for the purpose of understanding the development of the gear ratios, etc., it is preferred to consider the train including gear 14,-gear 22, gear 24, and gear 29. For the purposes of the explanation of the development of the design and the method employed therein assume that the gear 14 equals a; gear 22 equals 6; gear 24 equals 0; and gear 29 equals (Z. Now assume the train is locked and turned one turn positively, and as a whole without any relative motion between the gears. Then turn the gear a single turn in the reverse direction allowing the other gears to rotate at will. The resultant movement growing out of these two operations is expressed by the formula Solving this equation gives After considerable trial it was found that the two values which would give 2 when multiplied, and which yet would be so close to each other in value that the change in drive due to widely varying gear ratios would not be noisy, nor produce friction and vibration. These two values are 1.25 a 1.60 c T 01 3 and T 01 These ratios may be further expressed as follows 5 8 Z' and 5 are as follows,

d L2 52 45' These numbers will represent the number of teeth on the respective pairs of gears which will satisfy the requirement of the desired movement and yet result in the least friction, vibration, and noise.

When such ratios are not capable of having a common number into which they can be divided, the matter is solved in a slightly diiferent manner. For instance, the above ratios were 2 and 2 but suppose that for a given center distance t e ratios were such that it was impossible to find a common number which could be divided into two proper ratios which added would give the same number of teeth on the two sets of gears. For instance, in the above instance the number was 117 and the teeth numbers and ratios were It will be assumed that one set of gears has 117 teeth and the speed ratio is such that the other set can have only 100 teeth. But this number is insufiicient to satisfy the center distance requirement. It was discovered, however, that the diameters of these last two gears could be increased without increasing the number of teeth on them. This was done by twisting the teeth spirally. Thus, to determine the angle of the pitch of the spiral teeth take the number 117 as the diameter of a circle. Then take a line equal to the number 100 and place one end of it on one end of said diameter and swing the other end until it falls on the circumference. When this takes place, the angle found between the two lines will be found to be the pitch angle of the teeth. The relation is expressed by the equation If it is found that the pitch angle necessary to satisfy the center distance is too great for practical purposes then the both sets of gears can be made spiral the calculated pitch being split up proportionately.

It will therefore be understood that this invention has contributed at least very important innovations in the design of gearing and especially epicyclic gearing. The first is the highly satisfactory ratios for equal and opposite speed with minimum friction, noise, and vibration. The second is the possibility of spirally one or both sets of gears when otherwise the design of the gears Was impossible because the center distances and the speed ratios desired were such that no common number of teeth could be found for the respective sets of gears. Thus the invention has provided a simple compact and efficient design of gear trains especially epicyclic trains and which are quiet and substantially free from friction and vibration. These particular qualities are those highly desired in gear trains used for driving any parts of the mechanism of a motion picture apparatus Where quietness, lack of friction and vibration are very important requisites.

While the invention has been described in detail and with respect to a present preferred form thereof it is not to be limited to such details and forms since many changes and modifications may be made and the invention embodied in other forms and modifications without departing from the spirit and scope of the invention in its broadest aspects. Hence it is desired to cover any and all forms and modifications of the invention which may come within the language or scope of any one or more of the appended claims.

What is claimed is:

1. A compound epicyclic gear train for driving motion picture machine shutters which comprises a support, a pair of oppositely rotating shutter disks, a shaft mounted on said support on which one of said disks is fixed, the other disk being supported but rotatable upon said shaft, a gear fixed and movable with said second disk, a gear fixed stationary on said support with its center in line with the axis of said shaft, a pair of auxiliary shafts disposed on said first disk on the opposite sides of its center, gears on corresponding ends of said auxiliary shafts and meshing with said stationary gear and gears on the other corresponding ends of said auxiliary shafts and meshing with the gear fixed to the second disk.

cos. 0 equals 2. A compound epicyclic gear train for driving motion picture machine shutters which comprises a support, a pair of oppositely rotating shutter disks, a shaft mounted on said support on which one of said disks is fixed, the other disk being supported but rotatable upon said shaft, a gear fixed and movable with said second disk, a gear fixed stationary on said support With its center in line with the axis of said shaft, a pair of auxiliary shafts disposed on said first disk on the opposite sides of its center, gears 011 corresponding ends of said auxiliary shafts and meshing with said stationary gear and gears on the other corresponding ends of said auxiliary shafts and meshing with the gear fixed to the second disk, said sets of intermeshing gears adapted to have spiral teeth, the pitch of said teeth being calculated by the formula 0 cos. 0 equals E my hand.

AUGUSTO DINA. 

